The Largest Science Project You Have Never Heard Of

Well, speaking for myself anyway. The scientific enterprise in question is ITER, an international mega project based in southeastern France that seeks to create nuclear fusion, a potent source of energy that occurs only in the sun and other stars.

As one would imagine, trying to recreate what only these massive celestial bodies are known to do takes quite a lot of technological and scientific effort — hence the over $20 billion price tag, and the involvement of over thirty-five nations, including all twenty-six members states of the European Union, India, Japan,  China, Russia, South Korea and the United States.

An article from The Conversation, via Business Insider, offers a layman’s rundown of the nuclear fusion process:

Unlike fission, nuclei do not spontaneously undergo fusion: atomic nuclei are positively charged and must overcome their huge electrostatic repulsion before they can get close enough together that the strong nuclear force, which binds nuclei together, can kick in.

In nature, the immense gravitational force of stars is strong enough that the temperature, density and volume of the star’s core is enough for atomic nuclei to fuse through “quantum tunnelling” of this electrostatic barrier. In the laboratory, quantum tunnelling rates are far too low, and so the barrier can only be overcome by making the fuel nuclei incredibly hot – six to seven times hotter than the Sun’s core.

Even the easiest fusion reaction to initiate – the combination of the hydrogen isotopes deuterium and tritium, to form helium and an energetic neutron – requires a temperature of about 120 million C. At such extreme temperatures, the fuel atoms are ruptured into their component electrons and nuclei, forming a superheated plasma.

Keeping this plasma in one place long enough for the nuclei to fuse together is no mean feat. In the laboratory, the plasma is confined using strong magnetic fields, generated by coils of electrical superconductors which create a donut-shaped “magnetic bottle” in which the plasma is trapped.

Today’s plasma experiments such as the Joint European Torus can confine plasmas at the required temperatures for net power gain, but the plasma density and energy confinement time (a measure of the cooling time of the plasma) are too low to for the plasma to be self-heated.

But progress is being made – today’s experiments have fusion performance 1,000 times better, in terms of temperature, plasma density and confinement time, than the experiments of 40 years ago. And we already have a fair idea of how to move things to the next step.

Jumping off of this progress, ITER aims to demonstrate the vast scientific and technological applications of using fusion power for electricity generation.

The ITER reactor, now under construction at Cadarache in the south of France, will explore the “burning plasma regime”, where the plasma heating from the confined products of fusion reaction exceeds the external heating power. The total power gain for ITER will be more than five times the external heating power in near-continuous operation, and will approach 10-30 times for short durations.

The engineering and physical challenge is immense. ITER will have a magnetic field strength of 5 Tesla (100,000 times the Earth’s magnetic field) and a device radius of 6 m, confining 840 cubic metres of plasma (one-third of an Olympic swimming pool). It will weigh 23,000 tonnes and contain 100,000 km of niobium tin superconducting strands. Niobium tin is superconducting at 4.5K (about minus-269C), and so the entire machine will be immersed in a refrigerator cooled by liquid helium to keep the superconducting strands just a few degrees above absolute zero.

ITER is expected to start generating its first plasmas in 2020. But the burning plasma experiments aren’t set to begin until 2027. One of the huge challenges will be to see whether these self-sustaining plasmas can indeed be created and maintained without damaging the plasma facing wall or the high heat flux “divertor” target.

Again, this is very complex stuff: hence the fair amount of skepticism and criticism regarding the feasibility and technical challenges of recreating this process. Nevertheless, the first prototypes should be up and running by the 2030s, offering models for creating more commercially viable and environmentally sustainable power plants.

Given what is at stake — a reliable and efficient source of power for a fast-growing world with depleting fossil fuels — these hurdles are well worth pushing through.


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